Converter steelmaking process

Abstract

An improved converter steelmaking process that achieves a great increase in the refining capability of top-blown oxygen is provided. The process applies to an oxygen top-blowing converter that also permits bottom blowing of gas and it is characterized by supplying oxygen from a top-blowing lance and a bottom-blowing nozzle substantially throughout the refining operation, with 2 vol. % to less than 17 vol. % of a predetermined total oxygen flow rate being supplied from the bottom-blowing nozzle whereas the remaining part of oxygen is blown onto the surface of the hot metal from the top-blowing lance.

What is claimed is: 
     
       1. A steelmaking process comprising supplying oxygen from a top-blowing lance and a bottom-blowing nozzle substantially throughout the refining operation, with 2 vol% to 17 vol% of a predetermined total oxygen flow rate being supplied from the bottom-blowing nozzle whereas the remaining part of the oxygen is blown onto the surface of the melt from the top-blowing lance. 
     
     
       2. A process according to claim 1 wherein a mixture of oxygen and a slow-reactive gas is supplied from the bottom-blowing nozzle so that the total flow rate of bottom-blown gas is equal to 2 to 17 vol% of the predetermined total oxygen flow rate. 
     
     
       3. A process according to claim 1 wherein the oxygen supplied from the bottom-blowing nozzle is mixed with a slow-reactive gas only for a specified period of time. 
     
     
       4. A process according to claim 1 wherein the oxygen supplied from the bottom-blowing nozzle is replaced with a slow-reactive gas only for a specified period of time. 
     
     
       5. A process according to any of claims 1 to 4 wherein a relatively soft oxygen jet is blown onto the surface of the melt from the top-blowing lance throughout the period of the refining operation. 
     
     
       6. A process according to any of claims 1 to 4 wherein a relatively hard oxygen jet is blown in the initial stage of the refining operation and a relatively soft oxygen jet is blown in the final stage of the refining operation. 
     
     
       7. A process according to claim 1 wherein the force of oxygen blown onto the surface of the melt from the top-blowing lance is controlled by L/Lo where Lo: the depth (mm) of stationary hot metal when the coverter is in an upright position, L: the depth (mm) of penetration of top-blown oxygen jet. 
     
     
       8. A process according to claim 1 wherein lime is applied from the mouth of the converter within a specified period of the refining operation. 
     
     
       9. A process according to claim 1 wherein iron ores are supplied from the mouth of the converter within a specified period of the refining operation. 
     
     
       10. A process according to claim 1 wherein the oxygen flow rate, mixed gas flow rate or slow-reactive gas flow rate that is blown from the nozzle in the bottom of the furnace is equivalent to 2 to 13 vol% of the total oxygen supply. 
     
     
       11. A process according to any of claims 1 to 4 wherein the gas supplied from the bottom-blowing nozzle is free from lime. 
     
     
       12. A process according to any of claims 1 to 4 wherein both the gas supplied from the bottom-blowing nozzle and the oxygen supplied from the top-blowing lance are free from lime. 
     
     
       13. A process according to claim 1 comprising controlling the total iron of the slag to about 9 to 13 weight %.